Insulated-gate bipolar transistor (IGBT) devices are commonly used in high voltage applications, such as automotive ignition systems. For instance, IGBT devices may be used as coil drivers for automotive ignition control systems. In such applications, because IGBT devices have high input impedance, they may work/integrate well with Engine Control Module (ECM) integrated circuits (ICs), which are often implemented using complementary metal-oxide semiconductor processes.
IGBT devices implemented in automotive ignition systems generally operate at relatively high voltages (e.g., 400 V or more). Furthermore, such systems may operate in relatively harsh environments and, therefore, can be subject to failure as a result of these operating conditions (as well as other factors that may cause system failure). In some situations, failure of an IGBT in an automotive ignition system can cause catastrophic damage to elements of the system, and/or a vehicle in which the system is implemented. For instance, a shorted IGBT may overload a corresponding ignition coil. Such overloading of the coil may result in irreparable damage to the coil and could, in some instances, result in the ignition system causing an engine fire (e.g., due to the ignition coil combusting as a result of excessive current and associated heating in the ignition coil).
One approach to preventing such catastrophic failures (including the possibility of an engine fire) resulting from failure of an ignition control system (e.g., due to a shorted, or damaged IGBT) is to place a fuse between a battery terminal of the vehicle and one terminal of the primary winding of an ignition coil, where the other end of the primary winding is connected to a collector terminal of the IGBT (that operates as a coil driver). In such an arrangement, current in the fuse above a rated fuse value (e.g., as a result of such failure) will desirably cause the fuse to “open” or “blow” before catastrophic damage and/or a fire occurs.
Such approaches, however, have certain drawbacks. For example, fuses implemented in such systems can be slow to react and/or have unpredictable “open” points (e.g., a current and associated temperature at which the fuse “blows”). Such variation in a fuse's “open” point may be due to a number of factors, such as component packaging in which the fuse is housed, ambient operating conditions, and so forth, making it difficult to achieve precise fuse operation in the event of a failure in the system.
Also, if a fuse is slow to react, the goal of avoiding catastrophic damage may not be achieved. Furthermore, after such a failure (e.g., a blown fuse), the ignition control system will typically no longer function. Therefore, if the fuse blows as a result of a transient event, not a failure in the ignition control system, the vehicle may no longer function as desired (or at all) and need to be serviced.